1. Field of the Invention
The invention relates to an energy monitoring device, and particularly for monitoring the energy of a molecular fluorine laser emitting around 157 nm.
2. Discussion of the Related Art
In the past, i.e., prior to the investigations leading up to the present application, very little was known about the behavior of UV-photodetectors under long-term 157 nm laser pulse radiation exposure. Only a limited number of CW synchrotron exposure experiments had been done at Physikalisch-Technische Bundesanstalt, Berlin (PTB) and the National Institute of Standards and Technology (NIST).
Until now, no reliable energy monitor for detecting the pulse energy of a molecular fluorine (F2) laser emitting around 157 nm has been available. For detecting 193 nm and 248 nm excimer laser radiation, UV-photodetectors such as the International Radiation Detectors, Inc. (IRD) UVG 100 or the Hamamatsu S 5226 or S1226 have been used typically as energy monitor detectors. However, these detectors strongly degrade under 157 nm laser exposure.
It is therefore desired to have a reliable photodetector for monitoring pulse energies and/or another parameter of a molecular fluorine laser beam.